1. Field of the Invention
The present invention relates to polymeric multi-layer structures incorporating a layer of vinyl fluoride or vinylidene fluoride polymer bonded to a polar polymer layer and more particularly such multilayer structures in which the vinyl fluoride or vinylidene fluoride polymer is bonded to the polar polymer with the use of a polymeric adhesive.
2. Discussion of the Art
Vinyl fluoride polymers and vinylidene fluoride polymers are thermoplastic polymers which have a combination of useful properties and, especially, high chemical inertness and outstanding resistance to weather and to ultraviolet rays. As a result, they find many applications in a great variety of fields and, in particular, in protection against corrosion of ultraviolet rays. However, they have the disadvantage of being relatively costly, which probably restricts their outlets. A suitable means of reducing the cost of articles fabricated of a vinyl fluoride or vinylidene fluoride polymer consists in employing these polymers in the form of polymeric multilayer structures (films, sheets, plates, pipes, hollow bodies, and the like) in which they are combined with other polymers which, furthermore, contribute their own properties and advantages such as, for example, mechanical strength, sealability, impermeability, scratch resistance and the like. However, the abovementioned fluorine-containing polymers adhere very poorly to other polymers, with the result that it is generally necessary to make use of adhesives, which are in most cases polymeric, to ensure adhesive bonding between the fluorine-containing polymers and other polymers.
In French Patent No. FR-A-1,484,153 (The Dow Chemical Co.), it is recommended to bond a polyolefin layer to a fluorinated hydrocarbon polymer layer with the use of a polymeric adhesive consisting, preferably, of a copolymer of ethylene and vinyl acetate containing from approximately 13 to 35% by weight of vinyl acetate.
It has now been found that the use of such copolymers of ethylene and vinyl acetate to bond not a polyolefin but a polar polymer to a polymer of a fluorinated hydrocarbon, such as vinyl fluoride or vinylidene fluoride, gives multilayer complexes which are sensitive to delamination in the region of the fluorine-containing polymer layer.